The invention relates to a scanning device, for use in a magnetic instrument of the type using diagonal track scanning. In particular, reference is had to the aforementioned Peter Gunschmann application Ser. No. 685,381.
Generally, a high relative velocity is required between an electromagnetic transducer or magnetic tape head, and the magnetic tape is needed for wide band magnetic signals recorded on the magnetic tape. Typically, scanning systems have been developed wherein the magnetic heads are arranged on the periphery of a rapidly rotating head wheel and scan relatively slow moving magnetic tape at an angle with respect to the centerline of the magnetic tape. The stored information is recorded on the magnetic tape in a series of parallel track segments closely spaced apart from one another.
The high rate of speed at which the magnetic heads move across the magnetic tape require close contact between the magnetic heads and the magnetic tape in order to optimize signal transfer.
It has been found that the combination of the pressure exerted by the magnetic heads on the magnetic tape and the high speed at which the head wheel moves the magnetic heads over the magnetic tape results in a deterioration of the mechanical tolerances for proper operation. In practice, it is frequently necessary to change magnetic heads because the operation reduces the effectiveness.
Changing magnetic heads will not normally result in a properly aligned scanning device because of the high degree of accuracy required for positioning the magnetic heads with respect to the head disc. Normally, the head disc must be replaced and the magnetic heads readjusted.
In order to achieve proper relative adjustment between the magnetic heads and the head disc, the head wheel must be detached from the driving motor shaft and then reconnected after alignment. Because of the high precision required for proper alignment, these operations are carried out at the manufacturer's plant. Of course, this results in a loss of time and considerable costs. Furthermore, the head wheel is usually connected to the motor shaft of the driving motor so that is necessary to dismantle the entire scanning device to exchange magnetic heads.